In an existing OLED (Organic Light Emitting Diode) display device, each pixel unit includes at least three sub-pixels, each of which is driven by a pixel driving circuit. In order to satisfy the high requirement for Pixels Per Inch (PPI, the number of pixels per inch) of the OLED display device, pixel drive circuits with high-density are indispensable.
In an array substrate, a storage capacitor may be formed between the an active layer and a gate layer. However, when the active layer and the gate layer of the array substrate are fabricated, some impurities may remain on these layers, so that the flatness of the active layer and the gate layer is not good. At the opposite areas of the active layer and the gate layer (that is at the storage capacitor), the capacitor are likely to be abnormal due to the poor flatness of the active layer and the gate layer. For example, if two electrode plates of a capacitor are short-circuited or the capacitor is reduced, a certain voltage can cause a charge breakdown.
At present, the storage capacitor and the line size in the pixel driving circuit are basically on a micrometer level. In order to detect whether the storage capacitor is abnormal, a microscope is generally used. However, due to the limitation of the film layers of the capacitor, capacitor breakdown cannot be observed by the microscope, and thus it is hard to determine whether the capacitor is abnormal.